1. Field of the Invention
The present invention relates generally to piezoelectric generators and, more particularly, to piezoelectric generators for munitions fuzing.
2. Prior Art
All existing and future smart and guided gun-fired munitions and mortars that are equipped with electronics for fuzing or other similar purposes require electric power for their operation. The amount of power required for proper operation of certain components in gun-fired munitions, for example for the operation of certain fuzing electronics, is small enough to be provided by harvesting the electric charge generated directly from piezoelectric elements due to the firing acceleration induced straining. The advantage of using piezoelectric elements that can generate electric energy is that it eliminates the need for a primary battery and its related safety and shelf life problems. In general, such piezoelectric generators that harvest mechanical energy during the firing acceleration provide a very high degree of safety in munitions since they provide electrical energy that could operate onboard electronics only post firing. The use of reserve batteries for such very low power requirements is not cost effective and requires the allocation of valuable space and may face safety issues.
Current applications of piezoelectric elements of various designs and configurations such as stacks of piezoelectric ceramic, film layers, etc., which are loaded (strained) due to the firing acceleration in the axial direction, in bending, etc., and which may be equipped with appropriate inertial components to increase the generated loads (axial, bending, torsional, etc.), or are equipped with motion amplifying mechanisms to amplify the applied stains, have a common shortcoming that reduces their effectiveness as electrical energy generators and prevents efficient collection and storage of the generated charges. This shortcoming stems from the fact that during firing, the piezoelectric element is subjected to a very high level of acceleration induced impact type of forces during a very short period of time, in many cases of the order of one-tenth of a millisecond. As a result, the window for extraction and storage of the generated electrical charge is equally small, making efficient harvesting of the generated charge very difficult. The harvested charge is generally intended to be stored in a storage device such as a capacitor or used directly or conditioned to power a certain load.
A need therefore exists for new methods and devices that allow the aforementioned charges generated by piezoelectric elements due to the firing acceleration or other similar impact forces to be harvested over significantly longer periods of time, thereby allowing the generated charges to be harvested with significantly higher efficiency.
In addition, a need exists for new methods and devices that allow efficient harvesting of the aforementioned generated charges.